Golf club with flexible grip portion

ABSTRACT

A golf club shaft wherein the flexibility of the club over a short segment at the butt or grip end is increased in a controlled manner. A flexible hollow shaft insert of approximately 6.5 to 10 inches in total length having an insert stub portion of approximately 1.5 to 3 inches in length is fitted within the shaft, and an extension member of approximately 5 to 7 inches in length extends from the insert stub portion, the outer diameter of the extension member being greater than the outer diameter of the insert stub member, such that a shoulder is defined at the juncture. The shoulder is abutted against the butt end of the golf shaft, thereby creating a flex point whereby the extension portion flexes in a hinge-like angular manner relative to the golf club shaft. The extension portion is constructed to be substantially stiff or rigid, such that it remains substantially linear when bent relative to the golf shaft.

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/004,239, filed Dec. 20, 2007, claiming the benefit of U.S.Provisional Patent Application Ser. No. 60/876,817, filed Dec. 22, 2006.

BACKGROUND OF THE INVENTION

The different embodiments of the invention relate generally to the fieldof golf clubs, and more particularly to the field of golf club shaftshaving variations in flexibility along certain portions of the shaft,and even more particularly relate to golf club shafts wherein thevariation in flexibility occurs in the grip portion, and mostparticularly wherein the flexibility in the grip portion is localizedsuch that the flex performs in a hinge-like manner.

Steel and graphite composite golf club shafts both have a graduated bendwhen flexed. Shafts can be designed to be stiffer or more flexibledepending on the particular club, the ability of the golfer, etc. Theamount of bend in a standard golf shaft is gradually progressive, inthat the flex is greater near the tip end, i.e., the club head end, thannear the butt or grip end. The flex of the golf shaft enables the golferto generate increased club head speed, as the shaft bends and thenrecoils when striking the golf shot. Professional golfers use a stiffer,less flexible shaft because they can then attain the optimum distancewith more control. Most golfers, however, need a more flexible shaft inorder to maximize club head speed as the ball is struck—the key factorin driving distance. There is a trade-off, however, between power andcontrol, because the more flexible shafts, while increasing distance,have more twist or torque. Torque resistance is desirable in a golfshaft because most golfers do not hit the ball in the center of theclubface. When the ball is hit off-center toward the heel or toe of theclub head, the shaft twists and the ball is propelled to the left orright in an exaggerated and undesirable manner. Consequently, there is aneed to balance increased distance with loss of control.

The USGA in its “Rules of Golf” requires that at any point along thelength of the shaft, the shaft shall bend in such a way that thedeflection is the same regardless of how the shaft is rotated about thelongitudinal axis and shall twist the same amount in both directions. Inother words, there cannot be any preferential deflection in the shaft ina chosen direction, such as in the direction parallel to the perfectshot direction.

Standard golf shafts are tubular members of slightly diminishingdiameter progressing from the butt or grip end (the proximal end held bythe golfer) to the tip end (the end connected to the club head). Theflex of the shaft is determined primarily by the diameter of the shaft.If the diameter is wider throughout the shaft, it will be stiffer than ashaft constructed of similar material that is thinner in diameterthrough the shaft. The flex and torque of the shaft can be controlledmore in graphite shafts as opposed to metal shafts thorough selectivityand application of resins and carbon fiber materials. However, in thetraditional design, it is difficult for either steel or graphite shaftmakers to significantly alter the flex point of the shaft or createother desirable performance characteristics in a shaft.

Attempts to optimize golf club shaft design and structure can be seen inU.S. Pat. No. 5,842,930 to Koterba, U.S. Pat. No. 5,733,204 to Carrara,U.S. Pat. No. 2,250,429 to Vickery, U.S. Pat. No. 5,735,752 toAntonious, U.S. Pat. No. 6,024,651 to Cheng, U.S. Pat. No. 6,042,485 toCheng, U.S. Pat. No. 6,280,347 to Herber, U.S. Pat. No. 5,439,219 toVincent, U.S. Pat. No. 1,968,616 to Oldham, U.S. Pat. No. 3,809,403 toHunter, U.S. Pat. No. 5,322,290 to Minami, U.S. Pat. No. 6,582,320 toFendel, U.S. Patent Application Publication No. 2001/0012803 to Feeney,and U.S. Patent Application Publication No. 2002/0098907 to Hsu. Thesedevices have failed to provide an optimum solution to the problem ofbalancing control and distance.

For example, Koterba provides for a flexible cylindrical memberpositioned above the end of the golf club shaft, with a flexible gripmember coaxially mounted over the flexible member and the end of thegolf club shaft. The length of the flexible member is such that a flexpoint occurs between the hands of the golfer during the backswing. Withthis design however, all of the stress from the flexing occurs in thegrip member. Over time, this repeated flexing will result in failure ofthe grip member.

It is an object of this invention to provide a golf club wherein theflex is optimized relative to standard golf club shaft construction. Itis a further object to provide a golf shaft and club of improved flexand control wherein the improved flexibility occurs at or near theproximal end of the golf club, i.e., within the upper butt section orgrip portion of the club. It is a further object to provide a golf shaftand club of improved flex and control wherein the improved flexibilityoccurs between the upper and lower hands of the golfer gripping theclub. It is a further object to provide a golf shaft and club ofimproved flex and control wherein the flex is localized such that theflex performs in a hinge-like manner.

SUMMARY OF THE INVENTION

The invention is a golf club wherein the flexibility of the golf clubshaft at the butt or grip end is increased in a controlled manner byproviding a more flexible section along the butt end of the golf clubshaft.

In one embodiment, the flexible portion extends approximately 5 to 7inches in length. A flexible tubular shaft insert member ofapproximately 7 to 10 inches in length comprising an insert extensionportion approximately 5 to 7 inches in length and an insert taperedportion approximately 2 to 3 inches in length and of greater diameterthan the extension portion, is mated with the golf shaft. The taperedportion has an outer diameter sized and configured so as to correspondand mate with the inner diameter and internal tapering of the golf clubshaft. The tapered portion is inserted into the proximal end of theshaft such that the extension portion extends coaxially from the end ofthe golf shaft. A flexible sleeve is disposed about the insert extensionportion, the outer diameter of the flexible sleeve approximating theouter diameter of the golf club shaft, such that a standard grip may beapplied over the butt end of the shaft and the extension portion of theshaft insert. Preferably, the flexible tubular shaft insert is composedof a graphite composite material.

In a second embodiment, a one-piece tubular or hollow shaft insertmember of approximately 6.5 to 10 inches in length comprising anextension portion approximately 5 to 7 inches in length and an internalstub portion, preferably slightly tapered, approximately 1.5 to 3 inchesin length and of lesser diameter than the extension portion, is matedwith the golf shaft. The wall thicknesses and material of composition ofthe hollow shaft insert member are chosen such that the extensionportion flexes angularly relative to the golf shaft, in a hinge-likemanner, at the location of the junction between the extension portionand the end of the golf shaft, and further such that the extensionportion remains substantially linear when it is in the flexedorientation. The club grip member extends beyond the end of theextension portion and onto the golf shaft, with the grip member beingcomposed of a material more flexible than the extension portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of one embodiment of theimproved golf club.

FIG. 2 is a view of the flexible insert member of the embodiment of FIG.1.

FIG. 3 is a partial view of the golf club of the embodiment of FIG. 1,showing in dashed lines the extension portion of the flexible insertmember in the flexed state.

FIG. 4 is a partial cross-sectional view of another embodiment of theimproved golf club.

FIG. 5 is a view of the flexible insert member of the embodiment of FIG.4.

FIG. 6 is a partial view of the golf club of the embodiment of FIG. 4,showing in dashed lines the extension portion of the flexible insertmember in the flexed state.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawing, the invention will now be described indetail with, regard for the best mode and preferred embodiments. Ingeneral, the invention is an improved construction for a golf clubwherein the flexibility of the club at or near the butt end, i.e., atthe grip portion, is increased in a controlled manner.

In one embodiment, illustrated in FIGS. 1-3, the invention comprises aflexible tubular insert 30, preferably composed of a graphite compositematerial formed in a layered manner, the flexible insert 30 comprising atapered portion 31 and a tubular extension portion 32, preferablycylindrical, with an insert bore 33 extending the length of the flexibleinsert 30. The degree of flexibility in the flexible insert 30 andtherefore the degree of flexibility of the butt end portion of the golfclub may be varied by altering the material, pattern of layering,reinforcement material, bore size 33, etc., of the flexible insert 30.Other materials, such as carbon rods, fiberglass or materials withsimilar characteristics, may also be use to form the flexible insert 30.The flexible insert 30 may be formed as a single member, or the taperedportion 31 may be formed by positioning a tapered sleeve over one end ofa tubular rod, as shown in FIG. 1. The degree of taper in the taperedportion 31 is chosen to correspond with the tapering found in the bore12 of the golf club shaft 10 at its shaft butt end 11.

With the tapered portion 31 inserted into the shaft bore 12 and bondedusing suitable adhesives, the tubular insert extension portion 32extends coaxially beyond the butt end 11 of the golf club shaft 10. Theinner and outer diameters of the insert extension portion 32 preferablyapproximate the inner and outer diameters of the golf club shaft 10 atits tip, such that the insert extension portion 32 is much more flexiblethan the proximal portion of the golf shaft 10, due to the much greaterouter diameter of the golf shaft 10. A flexible cover sleeve 40 iscoaxially placed around the insert extension portion 32, the thicknessof the cover sleeve 40 being chosen such that its outer diametergenerally matches the outer diameter of the golf club shaft 10 at itsbutt end 11. In this manner, a standard grip member 20 and grip capmember 21 may be disposed on the golf club shaft 10 and flexible insert30 in known manner without resulting in any undesirable transitionshoulders or edges. The flexibility of the cover sleeve 40 may also bevaried in order to affect the flexibility of the flexible insert 30.Thus, the flexible cover sleeve 40 may be stiffer in order to reduce theflexibility of the flexible insert member 30, or the cover sleeve 40 maybe composed of material similar or even greater in flex characteristicsto the material composing the flexible insert 30 such that minimallimiting effect is created.

With this construction, the golf club has a flex range or bend profilebeginning at the location 34 where the insert extension portion 32 meetsthe shaft butt end 11 and extending to the end of the club, with theconstruction of the flexible insert member 30 allowing the flex todiffuse along the extension portion 32 such that excessive shear forcesare not present at the initial flex point 34. This construction allowsfor flex over the full length of the insert extension portion 32 andbetween the hands of the golfer. This creates a whip-like response inthe club as it is swung. The degree of flex can be controlled andoptimized relative to the strength and skill levels of individualgolfers. The shaft flex at the top of the golf swing can be increased by30 degrees over a standard golf shaft. The lightweight composition ofthe flexible shaft insert 30 does not adversely affect the balance ofthe club. In fact, the weight of the insert requires that someadditional weight be added to the club head in order to maintain thetraditional swing weight in the range of D1 to D5. This counterbalancingallows for a club head weight that can be about 15 to 20 grams heavier.The result of this additional club head mass is greater distance,assuming that the club head velocity increases as well. The physics isE=MV², where the increased mass times velocity squared translates intogreater distance for a golfer using this club.

While absolute dimensions will vary due to many factors, arepresentative flexible insert 30 may be between about 7 and 10 inchesin length, preferably about 7 to 8 inches. The tapered portion 31 willpreferably have a length of about 2 to 3 inches, and the insertextension portion 32 will preferably have a length of about 5 to 7inches. In a typical golf club shaft 10 having a wall thickness of about1/32 inches and an inner bore 12 of about 11/32 inches at its butt end11, the tapered portion 31 will have outer dimensions diminishing fromabout 16/32 to about 11/32 inches to match the taper of the shaft 10.The insert bore 33 is about 6/32 inches with a thickness of about 3/32inches on the extension portion 32, the extension portion 32 having anouter diameter of about 12/32 inches.

In another embodiment, illustrated in FIGS. 4-6, the invention comprisesa flexible hollow insert 70, preferably tubular and preferably composedas a one-piece bladder-molded member of a graphite composite material,the flexible insert 70 comprising an internal stub portion 71,preferably slightly tapered to match the taper of the golf club internalshaft bore 52, and an extension portion 32. The flexible hollow insert70 further comprises an internal hollow area 73. The hollow insert 70may be open on one end, open on both ends, or closed on both ends. Thedegree of flexibility in the flexible insert 30 and therefore the degreeof flexibility of the butt end portion of the golf club is controlledthrough choice of the material of composition, reinforcement material,wall thickness, etc., of the flexible insert 70. Other materials, suchas carbon rods, fiberglass or materials with similar characteristics,may also be use to form the flexible insert 70. Retention members 75,shown as annular ridges in FIG. 5, may be disposed on outer surface ofthe internal stub portion 71 to better fit and secure the internal stubportion 71 to the golf shaft 50. The internal stub portion 71 may bebonded, glued, heat welded or the like to permanently connect theinternal stub portion 71 to the golf shaft 50.

The outer diameter of the internal stub portion 71 is smaller than theouter diameter of the extension portion 72, such that a shoulder 76 isdefined. The internal stub portion 71 is fully inserted into the shaftbore 52 such that the shoulder 76 abuts the shaft butt end 51. The outerdiameter of the extension portion 72 adjacent the shoulder 76 is chosenso that it is substantially equal to the outer diameter of the shaftbutt end 51. The outer surface of the extension portion 72 is preferablytapered to correspond to the taper of the golf shaft 50, such that theouter diameter increases as the distance from the shoulder 76 increases.The extension portion 72 of the flexible insert member and a shortsegment of the golf shaft 50 are covered in known manner by a gripmember 60. The grip member 60 is more flexible than the extensionportion 72.

The flexible insert member 70 is designed and constructed such that aflex point 74 exists at the junction of the internal stub portion 71 andextension portion 72, such that the extension portion 72 is able to bendor flex in a hinge-like manner relative to the internal stub portion 71and golf shaft 50. The external portion 72 of the insert member 70 isdesigned and constructed to be substantially stiff or rigid, such thatit remains substantially linear when the extension portion 72 isangularly bent relative to the internal stub portion 71 and golf shaft50, as shown in FIG. 6.

With this construction, the stresses created by the bending movement areshared by the insert member 70 and the grip member 60, thereby greatlyincreasing the life of the club. The embodiment shown in FIGS. 4-6presents a relatively lightweight insert member 70, easily beingconstructed to have a total weight of 15 to 20 grams. This is useful inmaintaining a lower overall shaft weight, which is a desirable quality.

The flex point 74 occurs at a location between the hands of the golferwhen the club is being swung. During the upper backswing, the portion ofthe club containing the extension portion 72, i.e., the portion of theclub held by the upper hand of golfer, angularly bends at the flex point74 relative to the golf shaft 50 in a lever-like fashion. This resultsin increased club head speed in the down stroke because the lag and whipaction into the critical ball impact area is increased. An averagegolfer can now use a stiffer shaft 50 having greater torque resistance,resulting in better ball control, because of the higher club head speed.

It is contemplated that equivalents and substitutions for certainelements and structure set forth above may be obvious to those skilledin the art, and therefore the true scope and definition of the inventionis to be as set forth in the following claims.

1. A golf club comprising: a club shaft having a shaft bore and a buttend; a flexible hollow insert member mated with said club shaft, saidinsert member comprising an internal stub portion and an extensionportion, the junction of said internal stub portion and said extensionportion defining a shoulder, wherein said internal stub portion isinserted into said shaft bore such that said shoulder abuts said buttend and said extension portion extends coaxially from said butt end ofsaid club shaft, and wherein the outer diameter of said extensionportion is greater than the outer diameter of said internal stubportion, the outer diameter of said extension member adjacent saidshoulder corresponding to the outer diameter of said butt end; a gripmember coaxially mounted onto said extension portion and a portion ofsaid club shaft, said grip member being more flexible than saidextension portion; whereby said extension portion bends angularlyrelative to said club shaft and said internal stub portion, saidextension portion remaining substantially linear during such bending. 2.The club of claim 1, wherein said flexible tubular insert member iscomposed of a graphite composite material.
 3. The club of claim 1,wherein said insert member is approximately from 6.5 to 10 inches inlength, and wherein said insert stub portion is approximately about 1.5to 3 inches in length and said extension portion is approximately 5 to 7inches in length.
 4. The club of claim 1, further comprising retentionmembers disposed on said internal stub portion.
 5. The club of claim 4,wherein said retention members comprise annular ridges.
 6. The club ofclaim 1, wherein said internal stub portion and said extension portionare tapered.
 7. A golf club comprising: a club shaft having a shaft boreand a butt end; a flexible hollow insert member mated with said clubshaft, said insert member comprising an internal stub portion and anextension portion, the junction of said internal stub portion and saidextension portion defining a shoulder, wherein said internal stubportion is inserted into said shaft bore such that said shoulder abutssaid butt end and said extension portion extends coaxially from saidbutt end of said club shaft, and wherein the outer diameter of saidextension portion is greater than the outer diameter of said internalstub portion, the outer diameter of said extension member adjacent saidshoulder corresponding to the outer diameter of said butt end; a gripmember coaxially mounted onto said extension portion and a portion ofsaid club shaft, said grip member being more flexible than saidextension portion; said golf club having a flex point at the junction ofsaid internal stub portion and said extension portion, whereby saidextension portion bends angularly at said flex point relative to saidclub shaft and said internal stub portion, said extension portionremaining substantially linear during such bending.
 8. The club of claim7, wherein said flexible tubular insert member is composed of a graphitecomposite material.
 9. The club of claim 7, wherein said insert memberis approximately from 6.5 to 10 inches in length, and wherein saidinsert stub portion is approximately about 1.5 to 3 inches in length andsaid extension portion is approximately 5 to 7 inches in length.
 10. Theclub of claim 7, further comprising retention members disposed on saidinternal stub portion.
 11. The club of claim 10, wherein said retentionmembers comprise annular ridges.
 12. The club of claim 7, wherein saidinternal stub portion and said extension portion are tapered.
 13. A golfclub comprising: a club shaft having a shaft bore and a butt end; aflexible hollow insert member mated with said club shaft, said insertmember comprising an internal stub portion and an extension portion, thejunction of said internal stub portion and said extension portiondefining a shoulder, wherein said internal stub portion is inserted intosaid shaft bore such that said shoulder abuts said butt end and saidextension portion extends coaxially from said butt end of said clubshaft, and wherein the outer diameter of said extension portion isgreater than the outer diameter of said internal stub portion, the outerdiameter of said extension member adjacent said shoulder correspondingto the outer diameter of said butt end; a grip member coaxially mountedonto said extension portion and a portion of said club shaft, said gripmember being more flexible than said extension portion; said golf clubhaving a flex point at the junction of said internal stub portion andsaid extension portion, whereby said flex point is positioned betweenthe hands of a golfer when said golf club is in use; whereby saidextension portion bends angularly at said flex point relative to saidclub shaft and said internal stub portion, said extension portionremaining substantially linear during such bending.
 14. The club ofclaim 13, wherein said flexible tubular insert member is composed of agraphite composite material.
 15. The club of claim 13, wherein saidinsert member is approximately from 6.5 to 10 inches in length, andwherein said insert stub portion is approximately about 1.5 to 3 inchesin length and said extension portion is approximately 5 to 7 inches inlength.
 16. The club of claim 13, further comprising retention membersdisposed on said internal stub portion.
 17. The club of claim 16,wherein said retention members comprise annular ridges.
 18. The club ofclaim 13, wherein said internal stub portion and said extension portionare tapered.